Computer systems for training a machine learning model for preventing relay attacks. Including portable electronic devices capable of controlling the opening or closing, contactlessly, of an access to a road vehicle on the basis of a pretrained machine learning model. The general principle is based on the use of smartphones as a digital key for accessing a road vehicle. Machine learning is used to train a learning model capable of predicting the movement of a smartphone of this type as it approaches or moves away from the road vehicle. Subsequently, access to the road vehicle is authorized only when same receives the information on the movement of the smartphone.